Math help

[Broncmet724]

This is a dumbed down version of OBP since with some projections you don't get all the stats you need. I know it's not accurate, but it's not like projections are completely accurate anyway.

What I'm trying to figure out is walks. The simple formula is (Hits + BBs)/(ABs + BBs) = OBP. With one set of projectiona I have, they give me the Hits, ABs, and OBP, and I want to calculate BBs.

I've played with the formula, but it's been 20 years since I took math in high school and apparently I am more rusty than I thought. Can some give me the formula to figure out the BBs in this case knowing the other values?

BB = ?

[KCollins1304]

(Hits-AB*OBP)/(OBP-1)=walks

Did that pretty quick on a scratch sheet of paper, I'm pretty sure it's right though.

[bigh0rt]

The approximation of it is going to be BB = OBP(AB + BB) - H

But OBP only takes you out to the thousandths place on most sites, so it's not going to give you the exact number of BB.

e.g. Carlos Beltran (Career)

BB = .354(5113 + 591) - 1433
BB = .354(5704) - 1433
BB = 2019.216 - 1433
BB = 586.216

He's actually drawn 591 BB, but since OBP is rounded to the thousandths place, it's going to be an approximation. Either that or me not having my coffee this morning is killing my brain.

[Broncmet724]

(Hits-AB*OBP)/(OBP-1)=walks

Did that pretty quick on a scratch sheet of paper, I'm pretty sure it's right though.

Ok I get a negative value with that since ABs will be more than H, and OBP - 1 will be negative also.

[Broncmet724]

The approximation of it is going to be BB = OBP(AB + BB) - H

But OBP only takes you out to the thousandths place on most sites, so it's not going to give you the exact number of BB.

e.g. Carlos Beltran (Career)

BB = .354(5113 + 591) - 1433
BB = .354(5704) - 1433
BB = 2019.216 - 1433
BB = 586.216

He's actually drawn 591 BB, but since OBP is rounded to the thousandths place, it's going to be an approximation. Either that or me not having my coffee this morning is killing my brain.

Yep but the problem is the BBs in the middle of the parenthesis, I won't have the value for that. And I tried to carry it a bit further

BB = OBP * AB + OBP * BB - H
then
BB - OBP * BB = OBP * AB - H
then
BB - BB = OBP * AB - H / OBP

That's screwed up, but that's just me

Thanks for the help tho

[KCollins1304]

(Hits-AB*OBP)/(OBP-1)=walks

Did that pretty quick on a scratch sheet of paper, I'm pretty sure it's right though.

Ok I get a negative value with that since ABs will be more than H, and OBP - 1 will be negative also.

The numerator and denominator should both be negative, then they cancel each other out to give a positive number.

[Broncmet724]

(Hits-AB*OBP)/(OBP-1)=walks

Did that pretty quick on a scratch sheet of paper, I'm pretty sure it's right though.

Ok I get a negative value with that since ABs will be more than H, and OBP - 1 will be negative also.

The numerator and denominator should both be negative, then they cancel each other out to give a positive number.

True, but the first time I plugged the numbers in I got an obscene number of walks

I'll use one guy's projections of 173H 589AB .383OBP

(173-589*.383)/(.383-1)=BB

(-52.587)/(-.617) = BB

85 and change = BB

I assume I multiply the 589 * .383 first then subtract from the 173. It works out that way.

Thanks K

[bigh0rt]

Duh, I forgot to finish the equation

BB = (OBP*AB - H)/1 - OBP

should be the correct formula.

Using Beltran, again, we get...

BB = (.354*5113 - 1433)/1 - .354
BB = (1810.002 - 1433)/.646
BB = 377.002/.646
BB = 583.5944272
... which still isn't our desired 591, but again, I imagine that's likely due to the rounded OBP we used. His actual OBP is 0.35483871

Using that extended OBP, we get...
BB = 590.2327

EDIT: The discrepancy can be attributed to the calculator I'm using rounding itself after it runs out of places. I'm using a scientific and not a graphing.

[KCollins1304]

Duh, I forgot to finish the equation

BB = (OBP*AB - H)/1 - OBP

should be the correct formula.

Using Beltran, again, we get...

BB = (.354*5113 - 1433)/1 - .354
BB = (1810.002 - 1433)/.646
BB = 377.002/.646
BB = 583.5944272
... which still isn't our desired 591, but again, I imagine that's likely due to the rounded OBP we used. His actual OBP is 0.35483871

Using that extended OBP, we get...
BB = 590.2327

EDIT: The discrepancy can be attributed to the calculator I'm using rounding itself after it runs out of places. I'm using a scientific and not a graphing.

That's the same equation I gave him initially, just with the top and bottom multiplied by -1. It looks cleaner w/ yours though with the positive numbers.